Mechanical dispensers for viscous or extrudable materials include common, piston-type caulking guns found in any hardware store as well as small, hand-held devices for rolling up a flexible tube, such as the tubes that dispense toothpaste. Most extrudable material dispensers employ a piston attached to one end of an elongated piston rod. The piston is advanced through a partial-cylinder the shape of which is reminiscent of a trough and which is hereafter referred to as a holding cylinder or simply cylinder, the function of which is to hold a cylindrical canister of extrudable material.
Extrudable material in a canister is forced from the canister through a canister tip by driving a canister-internal piston installed into the “bottom” of the canister. The piston in the bottom of canister is hereafter referred to as a canister piston.
The canister piston drives extrudable material from the canister when the canister piston is driven through the canister by the piston attached to the piston rod. The piston rod is driven by a pistol grip mechanism that forms part of the dispenser. The pistol grip mechanism can be attached to either a ratcheting or ratchetless transmission device. Actuation of the pistol grip causes the piston rod to be advanced into the cylinder, which in turn drives the first piston (attached to the connecting rod) into the second piston (in the bottom of a canister of extrudable material) forcing extrudable material from the dispensing tube. As the first piston moves away from the transmission device and into the dispensing tube, extrudable material is forced from the tip of the canister.
FIG. 1 displays a side view of a typical prior art extrudable material dispenser described above. The first piston 21 in the cylinder is urged against the canister piston in the tube of extrudable material by operating the trigger 16, which is rotatably mounted in the handle 14. Grooves or teeth 17, formed in the elongated push rod 19 are engaged by a ratchet mechanism inside the handle 14 and not shown. The ratchet mechanism can be considered to be a “transmission” that converts the force applied to the trigger 16 into lateral displacement of the piston rod and first piston 21.
A problem with prior art caulking guns or other dispensers for extrudable materials is that the push rod 19 extends outwardly from the handle 14, which makes the dispenser unwieldy. The extended rod also makes the device difficult to store or set down between uses, especially when such devices are used in close quarters, as often happens when the devices are used in restaurants to dispense condiments and other extrudable food products.
A dispenser for dispensing extrudable material which eliminates the push rod 19 would be an improvement over the prior art.